CVE-2023-2829
📋 TL;DR
A vulnerability in BIND 9 DNS servers configured with DNSSEC validation and aggressive cache usage allows remote attackers to cause denial of service by sending specially crafted NSEC records. This affects organizations running vulnerable BIND versions as DNSSEC-validating recursive resolvers with specific configuration options enabled.
💻 Affected Systems
- ISC BIND 9
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote attackers can crash BIND DNS servers, causing complete DNS resolution failure for dependent systems and services.
Likely Case
Targeted DoS attacks against vulnerable DNS resolvers, disrupting DNS services for networks relying on them.
If Mitigated
Minimal impact if servers are patched or not using the vulnerable configuration options.
🎯 Exploit Status
Exploitation requires sending malformed NSEC records to vulnerable resolvers
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: BIND 9.16.42-S1, 9.18.16-S1, and later versions
Vendor Advisory: https://kb.isc.org/docs/cve-2023-2829
Restart Required: Yes
Instructions:
1. Download patched BIND version from ISC website
2. Stop BIND service
3. Install updated package
4. Restart BIND service
5. Verify service is running
🔧 Temporary Workarounds
Disable synth-from-dnssec
allDisable the aggressive DNSSEC cache usage option that triggers the vulnerability
Edit named.conf and remove or comment 'synth-from-dnssec yes;' line
🧯 If You Can't Patch
- Disable synth-from-dnssec option in BIND configuration
- Implement network controls to restrict DNS queries from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check BIND version with 'named -v' and verify configuration contains 'synth-from-dnssec yes;'Check Version:
named -vVerify Fix Applied:
Verify BIND version is 9.16.42-S1 or 9.18.16-S1 or later with 'named -v'📡 Detection & Monitoring
Log Indicators:
- BIND process crashes
- Unexpected termination messages in system logs
- Increased error logs related to NSEC processing
Network Indicators:
- DNS resolution failures
- Increased malformed DNS queries to resolvers
SIEM Query:
source="bind" AND ("crash" OR "terminated" OR "segmentation fault")